The invention relates to a prophylactic implant against fractures of osteoporosis-affected bone segments.
There are millions of osteoporotic persons in Germany alone, who most frequently have other diseases of the locomotor system.
Osteoporosis is accompanied by a loss of the bone mass, which exceeds the natural age-related bone disintegration. In addition, the quality of the microstructure of the bone tissue degrades. The loss of the bone mass, bone structure and function leads to clinical symptoms with lasting infirmities and fractures. Femoral neck fractures, fractures of the vertebral column and of the wrist are particularly widespread.
In the case of osteoporotic fractures of the femoral neck, the treatment at the present time mainly involves the complete resection of the femur and natural acetabulum, as well as the implantation of a complete artificial hip joint system. These systems are presently quite well developed, but this intervention should nevertheless be regarded as a severe intervention as has always been the case. In addition, as before, particularly critical is the long-term stability of the implant in the patient body. Influences on this have been, for example, the type of implant (with or without cementing), age and constitution of the patient, as well as many other parameters. Apart from this, it would be desirable if the total resection of bone segments could be deferred as long as possible, even in osteoporotic patients, or would become completely superfluous.
Starting points for an early diagnosis of the anticipated trauma or the fracture of the affected bone segment follow from modern radiological examinations. Signs of the osteoporosis-induced alterations in the bone structure can be clearly determined radiologically, and interestingly, the anticipated fracture can be predicted with astonishingly high accuracy within a period up to one year. This knowledge gives the opportunity and the chance to intervene therapeutically before the fracture occurs and to stop or retard the osteoporosis.
An implant, which can also be used for prophylactic purposes, is known from U.S. Pat. No. 2,537,070. The implant has a thin-walled reinforcing body with a plurality of passages in its outer wall. Pulverized bone material is pressed into the reinforcing body during the implantation. A contact between the spongiosa surrounding the implant and the pulverized bone material is allowed by the openings in the wall of the implant. A fixation should be achieved thereby through absorption of moisture through the surrounding bone structure.
From German published patent application DE-A-195 08 224 an implant is known which can be inserted as a prophylactic implant against fractures of osteoporosis-affected bone segments. This implant consists of a solid implant core forming a reinforcing core for the bone segment. The surface of the core member is coated with a surface layer of a dense or porous biocompatible material. The described implants are thought, in the first place, to repair defects which have already occurred, i.e., osteoporotic bones threatened by a fracture can possibly be protected beforehand. The above-mentioned early diagnosis of an anticipated trauma or the fracture still plays no role for the known implants.